Educational use only. Drug cards are AI-assisted study material for NCLEX preparation.
Gentamicin (Garamycin)
Mechanism of action
Binds the 30S ribosomal subunit, causing misreading of mRNA and bactericidal disruption of bacterial protein synthesis. Concentration-dependent killing (peak/MIC drives efficacy). Used for serious gram-negative infections — sepsis, pneumonia, complicated UTI, intra-abdominal infections — usually as part of combination therapy or extended-interval (once-daily) dosing.
Adverse effects
Life-threatening / NCLEX-tested
- Nephrotoxicity (acute tubular necrosis) — usually reversible if caught early
- Ototoxicity — both vestibular (vertigo, ataxia) AND cochlear (high-frequency hearing loss); often IRREVERSIBLE
- Neuromuscular blockade with concurrent neuromuscular blockers — risk of respiratory paralysis
- Hypersensitivity reactions, including rare anaphylaxis
Side effects
Common — what to teach
- Mild rash
- Mild GI upset
- Fever (drug fever)
- Tinnitus (early ototoxicity warning)
- Mild headache
Food & drug interactions
Loop diuretics (furosemide, bumetanide), vancomycin, cisplatin, and amphotericin B compound nephrotoxicity AND ototoxicity. Neuromuscular blockers (succinylcholine, rocuronium, vecuronium) plus aminoglycosides can cause prolonged neuromuscular blockade. Penicillins and cephalosporins synergize for severe gram-positive infections (e.g., enterococcal endocarditis).
Nursing implications
Assessment, monitoring, patient teaching
- Monitor peak (30 minutes after end of infusion) and trough (just before next dose) levels — therapeutic peak ~5–10 mcg/mL (8–10 for severe infection), trough < 2 mcg/mL; for once-daily dosing, monitor a single random level per protocol
- Baseline and every 2–3 days: BUN, creatinine, urine output
- Baseline audiology if planned course > 7–10 days; teach patients to report tinnitus, hearing changes, or vertigo IMMEDIATELY
- Infuse over 30–60 minutes, never push
- Adjust dose for renal function — extended-interval dosing protocols rely on accurate CrCl
- Two-nurse verification for serious infection dosing — high-alert medication
- Maintain adequate hydration to limit nephrotoxicity
When to hold / contraindications
- Trough level above target (renal accumulation) — extend the interval before next dose
- Acute kidney injury or rising creatinine
- New tinnitus, hearing change, or vertigo — assess and discuss with provider before next dose
- Pregnancy (relative — fetal ototoxicity risk; use only if benefit outweighs)
- Concurrent neuromuscular blockade in OR setting without anesthesia direction
Memory anchor
Aminoglycosides hit "the 8th cranial nerve and the kidney" — ototoxicity (often permanent) and nephrotoxicity (often reversible). Peak 30 min after, trough just before. Avoid stacking with vanco/loop diuretics.
Practice Gentamicin questions
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